1. Field of the Invention
The present invention relates to an electric zero-turn working vehicle, such as a lawn mower, equipped with a pair of right and left electric motors for driving respective right and left drive wheels, and equipped with an electric motor for driving a working implement, such a mower unit.
2. Background Art
An electric tractor disclosed by JP 2002-356116 A, serving as a typical electric working vehicle, is equipped with a battery, a traveling electric motor, and a PTO (power take-off) electric motor. The traveling electric motor is supplied with electric power from the battery to drive right and left drive wheels. The PTO electric motor is also supplied electric power from the battery to drive a PTO shaft for driving a working implement. The electric tractor is advantageously lightened because the battery, the traveling electric motor and the PTO electric motor are light in comparison with an engine and implements surrounding the engine, e.g., a radiator and a muffler. Further, the electric tractor is advantageous in environmental protection because it is free from problems accompanied with an engine, e.g., emission, noise and vibration.
A lawn mower disclosed by JP 2007-153130 A, serving as a typical zero-turn working vehicle, is equipped with a pair of right and left transaxles for driving respective right and left drive wheels, and is equipped with a PTO shaft for driving blades in a mower unit, serving as a working implement attached to the vehicle. The right and left transaxles support respective axles of the right and left drive wheels, and can be differentially driven for zero-turn of the lawn mower. This lawn mower is equipped with an engine for driving the right and left transaxles and the PTO shaft. More specifically, an output shaft of the engine is drivingly connected via a belt transmission to input shafts of the respective right and left transaxles, and is extended to serve as the PTO shaft that is drivingly connected via another belt transmission to the blades of the mower unit. The right and left transaxles are compact so as to miniaturize the lawn mower, however, a space between the right and left transaxles can be large enough to arrange a grass duct connected to the mower unit.
An electric zero-turn working vehicle, such as a lawn mower, is desired to have a pair of right and left electric motors for driving respective right and left drive wheels in consideration of the above-mentioned electric tractor that is advantageous in reduction of weight and in environmental protection, and in consideration of the above-mentioned lawn mower that is advantageous in its zero-turn performance. When the above-mentioned zero-turn lawn mower is intended to have right and left electric motors for driving respective right and left drive wheels, it is noticeable that the pair of right and left transaxles supporting respective axles of the right and left drive wheels should include the right and left electric motors, respectively.
Here, a problem arises that a relatively heavy PTO electric motor for driving a working implement may adversely affect the balance of the vehicle if the PTO electric motor is disposed adjacent to the working implement, such as a mower unit, that is distant from the right and left transaxles adjacent to the right and left drive wheels. On the contrary, if the PTO electric motor is distant from a working implement, for example, if the PTO electric motor is disposed above one of front and rear portions of a vehicle body frame, and a mower unit serving as the working implement is disposed below the other of front and rear portions of the vehicle body frame, loss of power transmitted from the PTO electric motor to the working implement may increase or the PTO electric motor may have to increase its capacity for covering the power loss.